正常人左心室功能指标的参考值及其预计公式的初步研究报告*

目的: 当前评估左心室容量和功能仍常用正常值范围,个体化分析也仅使用体表面积进行校正。尚缺少个体化因素相关的大样本参考值和预计公式。方法: 本研究纳入美国加州洛杉矶县南湾地区1200名健康志愿者,其中男807女393,年龄20岁-94岁,心脏CT造影（CTA）,经过高精度三维成像技术处理,计算左心室容积在收缩和舒张过程中的连续动态变化,测定左心室（LV）容量和功能指标：舒张末期容积（EDV)、收缩末期容积(ESV)、每搏输出量(SV)、射血分数(EF)和心输出量(CO)。将以上指标与一般特征指标进行多因素相关分析,以探索正常人预计值计算公式。结果: 男性除LVEF小于女性外（P<0.001）,其余各指标均大于女性（P<0.001）。多元线性回归分析提示, 性别、年龄、身高和体质量均为EDV、ESV、SV的独立影响因子(P<0.001); 而CO仅受年龄、性别、体质量显著影响(P<0.001),但与身高无关(P>0.05)。CO的预测公式CO (L·min^-1)= 6.963+0.446(Male) -0.037×年龄(yr)+0.013×体质量(kg)。结论: 性别、年龄、身高、体质量均影响左心室容量和功能,建立预测值计算公式,对心血管疾病的无创评估和个体化精准医疗具有重要参考价值。     

Analysis of spike electrogenesis of Eel electroplaques with phase plane and impedance measurements

Eel electroplaques provide experimental conditions in which registration of phase plane trajectories (dV/dt vs. V) and impedance measurements with an AC Wheatstone bridge, in conjunction with spike electrogenesis describe quantitatively the ionic processes of the electrogenesis. Thus, these data employing as they do measurements of transients, permit an independent test of the validity of the assumptions which underlie the Hodgkin-Huxley equivalent circuit: independent ionic channels with fixed ionic batteries and exhibiting time-variant conductance changes with different kinetics for the different channels. The analysis accords with earlier findings on voltage-clamped electroplaques and this agreement confirms the validity of the equivalent circuit despite the fact that the current-voltage characteristics of the axons and electroplaques differ profoundly. As for squid axons, the equivalent circuit of the electroplaques has four branches: a capacity and three ionic channels. One of the latter is an invariant leak channel (G_L) of high conductance. A K channel (G _K) is fully open at rest, but rapidly undergoes inactivation when the cell is depolarized by more than 40 mv. G_L and G _K have a common inside negative emf (E _K). A Na channel (G _Na) with an inside positive emf (E _Na) is closed at rest, but opens transiently upon depolarization.     

Cross-reactions between tryptic polypeptides of staphylococcal enterotoxins B and C.

The strong cross-reactions demonstrated for staphylococcal enterotoxins B (SEB) and C1 (SEC1) by measurement of antigen-binding capacity were reflected in well defined polypeptides obtained by limited tryptic digestion from SEB and SEC1. Two antigenic determinants on each enterotoxin were capable of reacting with heterologous antibody, one on the first 57 amino acids and one on the last 150 residues of the polypeptide backbone. The larger, carboxyl terminal polypeptides bound efficiently to homologous antiserum but about two orders of magnitude less efficiently to heterologous antibody. The amino terminal peptides showed only weak homologous binding but nearly comparable heterologous binding. It is proposed that the determinant on the amino terminal polypeptides is largely responsible for the strong reciprocal binding of the intact enterotoxins and that their low antigen-binding capacity is due to a random or a structurally distorted conformation in solution.     

The topological nature of tag jumping in environmental DNA metabarcoding studies

Metabarcoding of environmental DNA constitutes a state-of-the-art tool for environmental studies. One fundamental principle implicit in most metabarcoding studies is that individual sample amplicons can still be identified after being pooled with others—based on their unique combinations of tags—during the so-called demultiplexing step that follows sequencing. Nevertheless, it has been recognized that tags can sometimes be changed (i.e., tag jumping), which ultimately leads to sample crosstalk. Here, using four DNA metabarcoding data sets derived from the analysis of soils and sediments, we show that tag jumping follows very specific and systematic patterns. Specifically, we find a strong correlation between the number of reads in blank samples and their topological position in the tag matrix (described by vertical and horizontal vectors). This observed spatial pattern of artefactual sequences could be explained by polymerase activity, which leads to the exchange of the 3′ tag of single stranded tagged sequences through the formation of heteroduplexes with mixed barcodes. Importantly, tag jumping substantially distorted our data sets—despite our use of methods suggested to minimize this error. We developed a topological model to estimate the noise based on the counts in our blanks, which suggested that 40%–80% of the taxa in our soil and sedimentary samples were likely false positives introduced through tag jumping. We highlight that the amount of false positive detections caused by tag jumping strongly biased our community analyses.     

The appropriate use of regression equations for the estimation of segmental inertia parameters

Linear regression equations are commonly used in conjunction with experimental data to provide linear relationships between quantities which are dimensionally distinct. In many cases theoretical relationships between such quantities are known and can be used as a basis for non-linear regression equations. This study compares linear and non-linear approaches for estimating the segmental moments of inertia from anthropometric measurements using the data of Chandler et al. [Chandler et al. (1975) Investigation of inertial properties of the human body. AMRL Technical Report 74-137, Wright Patterson Air Force Base. OH.] Right limb data were used to derive the equations while left limb data were used as a cross-validation sample to evaluate the inertia estimates calculated from the equations. For the limb segments the standard error estimates had average values of 21% for the linear equations and 13% for the non-linear equations. Data on a 10 yr-old boy was used to compare the two approaches outside the sample range. The mean percentage residuals were 286% for the linear equations and 20% for the non-linear equations. A set of non-linear equations is provided.     

Systematic accuracy and precision analysis of video motion capturing systems--exemplified on the Vicon-460 system

With rising demand on highly accurate acquisition of small motion the use of video-based motion capturing becomes more and more popular. However, the performance of these systems strongly depends on a variety of influencing factors. A method was developed in order to systematically assess accuracy and precision of motion capturing systems with regard to influential system parameters. A calibration and measurement robot was designed to perform a repeatable dynamic calibration and to determine the resultant system accuracy and precision in a control volume investigating small motion magnitudes (180x180x150mm(3)). The procedure was exemplified on the Vicon-460 system. Following parameters were analyzed: Camera setup, calibration volume, marker size and lens filter application. Equipped with four cameras the Vicon-460 system provided an overall accuracy of 63+/-5mum and overall precision (noise level) of 15mum for the most favorable parameter setting. Arbitrary changes in camera arrangement revealed variations in mean accuracy between 76 and 129mum. The noise level normal to the cameras' projection plane was found higher compared to the other coordinate directions. Measurements including regions unaffected by the dynamic calibration reflected considerably lower accuracy (221+/-79mum). Lager marker diameters led to higher accuracy and precision. Accuracy dropped significantly when using an optical lens filter. This study revealed significant influence of the system environment on the performance of video-based motion capturing systems. With careful configuration, optical motion capturing provides a powerful measuring opportunity for the majority of biomechanical applications.     

The influence of bone damage on press-fit mechanics

Press-fitting is used to anchor uncemented implants in bone. It relies in part on friction resistance to relative motion at the implant–bone interface to allow bone ingrowth and long-term stability. Frictional shear capacity is related to the interference fit of the implant and the roughness of its surface. It was hypothesised here that a rough implant could generate trabecular bone damage during implantation, which would reduce its stability. A device was constructed to simulate implantation by displacement of angled platens with varying surface finishes (polished, beaded and flaked) onto the surface of an embedded trabecular bone cube, to different nominal interferences. Push-in (implantation) and Pull-out forces were measured and micro-CT scans were made before and after testing to assess permanent bone deformation. Depth of permanent trabecular bone deformation (‘damage’), Pull-out force and Radial force all increased with implantation displacement and with implantation force, for all surface roughnesses. The proposed hypothesis was rejected, since primary stability did not decrease with trabecular bone damage. In fact, Pull-out force linearly increased with push-in force, independently of trabecular bone damage or implant surface. This similar behaviour for the different surfaces might be explained by the compaction of bone into the surfaces during push-in so that Pull-out resistance is governed by bone-on-bone, rather than implant surface-on-bone friction. The data suggest that maximum stability is achieved for the maximum implantation force possible (regardless of trabecular bone damage or surface roughness), but this must be limited to prevent periprosthetic cortical bone fracture, patient damage and component malpositioning.     

Immunocytochemical demonstration of vimentin in astrocytes and ependymal cells of developing and adult mouse nervous system

The occurrence of vimentin, a specific intermediate filament protein, has been studied by immunoflourescence microscopy in tissue of adult and embryonic brain as well as in cell cultures from nervous tissue. By double imminofluorescence labeling, the distribution of vimentin has been compared with that of subunit proteins of other types of intermediate filaments (glial fibrillary acidic [GFA] protein, neurofilament protein, prekeratin) and other cell-type specific markers (fibronectin, tetanus toxin receptor, 04 antigen). In adult brain tissue, vimentin is found not only in fibroblasts and cells of larger blood vessels but also in ependymal cells and astrocytes. In embryonic brain tissue, vimentin is detectable as early as embryonic day 11, the earliest stage tested, and is located in radial fibers spanning the neural tube, in ventricular cells, and in blood vessels. At all stages tested, oligodendrocytes and neurons do not express detectable amounts of vimentin. In primary cultures of early postnatal mouse cerebellum, a coincident location of vimentin and GFA protein is seen in astrocytes, and both types of filament proteins are included in the perinuclear aggregates formed upon exposure of the cells to colcemid. In cerebellar cell cultures of embryonic-day-13 mice, vimentin is seen in various cell types of epithelioid or fibroblastlike morphology but is absent from cells expressing tetanus toxin receptors. Among these embryonic, vimentin-positive cells, a certain cell type reacting neither with tetanus toxin nor with antibodies to fibronectin or GFA protein has been tentatively identified as precursor to more mature astrocytes. The results show that, in the neuroectoderm, vimentin is a specific marker for astrocytes and ependymal cells. It is expressed in the mouse in astrocytes and glial precursors well before the onset of GFA protein expression and might therefore serve as an early marker of glial differentiation. Our results show that vimentin and GFA protein coexist in one cell type not only in primary cultures in vitro but also in the intact tissue in situ.     

Relationship between physical,biochemical and biomechanical properties of tissue-engineered cartilage-carrier-constructs

Three-dimensional cartilage-carrier-constructs were produced according to a standard protocol from chondrocytes of an adult mini-pig. Physical parameters (height and weight) correlated very well with total DNA content (r²=0.86, re. 0.94). The relation between DNA content and glycosaminoglycan content was less but still significant. No significant relationship was found between the elasticity module and the DNA content, even if the elasticity module increased slightly at higher DNA content. With respect to later implantation, selection of a construct for implantation based on the weight, which can be determined non-invasive and under sterile conditions, seems to be justifiable.Revisions requested14 October 2004; Revisions received 7 December 2004     

Water jet cutting for bones and bone cement--parameter study of possibilities and limits of a new method]

Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p < 0.05). Adding a water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p < 0.05), but selectivity is lost, although the differences in cutting depth between the two materials was significant (p < 0.05). With an abrasive, the quality of the cut was better for both materials. The water jet technology--in particular the abrasive technique--can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the "depth control" of the jet.